A variety of commercial products employ fabrics as a reinforcement medium, for example, tires, power transmission belts, conveyor belts, and the like. These products are typically constructed of layers of fabric impregnated with and/or intimately surrounded by an elastomeric polymer matrix. The fabric thus serves to reinforce the resulting elastomeric product.
In many applications, lateral support for the product is important. That is, the product should be substantially inextensible in one direction yet capable of elongation in another direction. In the past, it has been proposed that a fabric using relatively inextensible inlaid warp yarns with an extensible weft insertion yarn provides greater flexibility in the weft direction (see, published U.K. Application No. 2,102,849). Similarly, U.S. Pat. No. 4,427,107 to Roberts et al suggests having different stretch characteristics in the warp and weft directions with fibers having a warp to weft elongation ratio in the range of between 1:2 and 1:3. (See also, U.S. Pat. Nos. 4,370,784 to Turnbull; 4,514,179 to Skura; 3,872,735 to Hnatec.)
While provision of a relatively extensible yarn in one direction and a relatively inextensible yarn in another direction in fabric constructions employed as a reinforcing medium in a polymer matrix does afford an amount of elongation potential in a desired direction, oftentimes the exact amount of extension is, in practice, more/less than that desired. Accordingly, what has been needed is an elastomer-coated fabric whereby the amount of potential elongation in one of the directions thereof is closely controlled so that more accurate extension potential properties can be imparted to the resulting product in which it is employed. it is toward attaining such a product that the present invention is directed.
According to this invention, an elastomer-coated fabric product is provided which is useful as a reinforcing medium in a variety of end use applications employing the same (e.g., tires, power transmission belts, conveyor belts, etcetera). The elastomer-coated fabric product of this invention is preferably a warp-knit, weft-inserted fabric whereby the warp yarns exhibit a predetermined elongation potential in the fabric's machine direction. Additional elongation potential for the fabric is provided by this invention in the machine direction by maintaining the fabric in a compressed state. That is to say, during processing, the fabric is compressed within its plane without buckling, and this compressed state is maintained by means of the dried elastomer coating. Thus, not only do the warp knit yarns themselves contribute to the elongation potential for the resulting elastomer-coated fabric, but the amount of fabric compression can also be preselected and controlled in such a manner that the total elongation potential for the resulting fabric is within close tolerances of that desired (e.g., within about plus or minus 2%).
The fabric of this invention is preferably produced by coating a liquid elastomer onto the fabric so that it at least partially impregnates the same and then compressing the fabric to the desired extent. Alternately, the fabric may be compressed prior to the application of the liquid elastomer coating. The liquid-coated and compressed fabric is then dried so as to solidify the elastomer coating thereon and thus maintain the fabric in its compressed state. Compression of the fabric is conveniently accomplished by overfeeding the fabric to a conventional tenter frame--that is, the rate at which the fabric is fed to the tenter frame is greater than the tenter frame's operating rate.
These as well as other objects and advantages will become more clear after carefully considering the detailed description thereof which follows.